1. Field of the Invention
The present invention relates to an air bag system for vehicles, and more particularly to a passenger air bag system for vehicles, which is capable of preventing eccentric expansion of a cushion when a collision of the vehicle occurs by improvement of the structure of the cushion.
2. Description of the Related Art
Generally, an air bag system for vehicles is mounted in front of a driver seat or a passenger seat in such a manner that a cushion of the air bag system is instantly expanded when a collision of the vehicle occurs for protecting a driver or a passenger from injury.
The air bag systems may be classified into a driver air bag system and a passenger air bag system. The driver air bag system is mounted to the steering wheel of the vehicle for protecting the driver from injury. The passenger air bag system is mounted to an instrument panel of the vehicle disposed in front of the passenger seat for protecting the passenger from injury. Basically, the driver air bag system is requisite, and the passenger air bag system is optional; however, vehicles with passenger air bag systems basically mounted therein for protecting passengers from injury are on the increase in recent years.
FIG. 1 is an exploded perspective view showing a conventional passenger air bag system, FIG. 2 is a longitudinal sectional view showing the conventional passenger air bag system, and FIG. 3 is a perspective view, partially cutaway, showing a cushion of the conventional passenger air bag system.
As shown in FIGS. 1 to 3, the conventional passenger air bag system for vehicles comprises: an air bag housing 4 mounted to an instrument panel 2; an inflator 6 attached to the rear part of the air bag housing 4 for discharging gas when a collision of the vehicle occurs; a cushion 8 accommodated in the front part of the air bag housing 4 such that the cushion 8 is expanded to the front of a passenger seat by means of gas discharged from the inflator 6; and a retainer 10 attached to the air bag housing 4 for supporting the cushion 8, the retainer 10 having a plurality of gas-guiding holes 10a for guiding gas discharged from the inflator 6 to the cushion 8.
The air bag housing 4 comprises: a cushion housing 12 formed in the shape of a box with the front part opened so that the cushion 8 is accommodated in the cushion housing 12 while being folded; and a can housing 14 connected to the rear part of the cushion housing 12, in which the inflator 6 is disposed.
The cushion housing 12 is provided along both longitudinal sides at the front part thereof with flanges 12a, respectively, which are fixed to the rear part of the instrument panel 2 by means of bolts. The can housing 14 is connected to the rear part of the cushion housing 12 in such a manner that the can housing 14 communicates with the cushion housing 12. The can housing 14 is fixed to a cowl cross member (not shown) disposed in the instrument panel 2 by means of a mounting bracket (not shown).
The inflator 6 is formed in the shape of a cylinder. The inflator 6 is provided on the outer circumference at one side thereof with a plurality of gas-discharging holes 16 for discharging gas when a collision of the vehicle occurs.
At one end of the inflator 6 is formed a fixing protrusion 18 having a male screw thread part formed on the outer circumference thereof, on which a fixing nut 20 is rotatably fitted so that the inflator 6 is attached to the side of the can housing 14. At the other end of the inflator 6 is formed a connector-connecting member 22 in such a manner that the connector-connecting member 22 is protruded outwardly. To the inflator 6 is connected a connector 24, by which the inflator 6 is linked to an external device, through the connector-connecting member 22.
As shown in FIG. 3, the cushion 8 comprises: a main panel 28 formed in the shape of a cylinder and having an inlet part 26 formed at one side thereof, the inlet part 26 of the main panel 28 being fixed to the can housing 14 by means of the retainer 8; side panels 30 attached to both open sides of the main panel 28 by means of sewing, respectively; and a tether 32 having one end fixed to the inlet part 26 of the main panel 28 and the other end fixed to the inner side of the main panel 28, which is opposite to the inlet part 26 of the main panel 28.
The main panel 28 is formed in such a manner that a long strip is rolled in the shape of a cylinder and then stitched. The main panel 28 is the front part of the cushion 8, which approaches a passenger when the cushion 8 is expanded. To the sides of the main panel 28 are attached the side panels 30 by means of sewing, respectively.
Each of the side panels 30 has a ventilation hole 30a formed at a prescribed part thereof for discharging gas introduced into the cushion 8 to the outside. When the passenger contacts the cushion 8 due to the impact caused when a collision of the vehicle occurs, the gas in the cushion 8 is discharged to the outside through the ventilation hole 30a so that shock transmitted to the passenger is effectively absorbed.
The tether 32 is formed in the shape of a long strip. One end of the tether 32 is fixed to the inlet part 26 of the main panel 28, and the other end of the tether 32 is fixed to the inner side of the cushion 8 opposite to the inlet part 26 of the main panel 28, by which the shape of the expanding cushion 8 is determined.
Specifically, both ends of the tether 32 are fixed to the inlet part 26 and the front part of the cushion 8, whereby the expanded length of the cushion 8 is restricted. Consequently, it is possible to prevent a bag slip phenomenon in which the passenger is injured due to the expanding pressure of the cushion 8.
The retainer 10 is attached to the can housing 14 together with the cushion 8 by means of bolts such that the plurality of gas-guiding holes 10a formed at the center of the retainer 10 communicate with the inlet part 26 of the cushion 8. The retainer 10 serves to support the cushion 8 so that the cushion 8 is not separated from the can housing 14 due to the pressure of the gas when the cushion 8 is expanded.
The operation of the conventional passenger air bag system with the above-stated construction will now be described. When a collision of the vehicle occurs, an operation signal is transmitted to the inflator 6 via the connecter 24, and then the inflator 6 is exploded by means of electric current supplied to the inflator 6 for discharging gas through the gas-discharging holes 16.
The gas discharged from the inflator 6 flows along the can housing 14 so that the gas is supplied into the cushion 8 through the gas-guiding holes 10a of the retainer 10. The cushion 8 is expanded to the front of the cushion housing 12 by means of the gas supplied into the cushion 8.
The instrument panel 2 is broken by means of the cushion 8 expanded as described above. Subsequently, the cushion 8 is expanded toward a passenger seated in the passenger seat, whereby shock transmitted to the passenger is effectively absorbed, and thus injury to the passenger is minimized.
In the conventional passenger air bag system for vehicles, however, the inflator 6 is horizontally disposed in the can housing 14, and the gas-discharging holes 16 are provided adjacent to one end of the inflator 6. As a result, the cushion 8 is eccentrically expanded by means of the gas discharged from the inflator 6 when a collision of the vehicle occurs.
In order to solve the eccentric expansion of the cushion 8 as described above, there has been proposed a method for modifying the gas-guiding holes 10a of the retainer 10 recently. Specifically, the plurality of gas-guiding holes 10a with different sizes are formed at the retainer 10 while being appropriately arranged so that the gas discharged from the inflator 6 is uniformly supplied to the cushion 8 while the gas flows through the gas-guiding holes 10a of the retainer 10, whereby the eccentric expansion of the cushion 8 is prevented.
In the case that the shapes of the gas-guiding holes 10a of the retainer 10 are changed in order to prevent the eccentric expansion of the cushion 8, however, it is required that a plurality of new retainers 10 be manufactured depending upon various kinds of air bag systems, and thus a plurality of molds, which are used for the respective retainers 10, become necessary. Consequently, the cost and time of manufacturing retainers are increased. The cost of testing the manufactured retainers is also incurred.
Furthermore, the retainer 10 causes flow resistance when the gas discharged from the inflator 6 passes through the gas-guiding holes 10a of the retainer 10. As a result, the time required to fully expand the cushion 8 is increased.